Preforms are well known in the art. Preforms are typically injection molded. In a later operation the preform is blow molded to the final shape, often with the assistance of a stretch rod.
Preforms may be nested, so that an inner preform is disposed within an outer preform. This arrangement provides the benefit that both preforms may be blow molded at the same time and in a single operation. A separate operation to insert one preform inside another is necessary.
The two, or more, preforms may be injection molded in separate operations, requiring assembly to nest the preforms for the single blow molding operation. But assembly, in order to nest the preforms, may occur at a first location. The nested preforms may be shipped to a second location, miles away, for warehousing or blow molding. If warehoused, the nested preforms may be subjected to thermal cycling, and likely shipped again for blow molding. In preparation for the blow molding operation, the nested preforms may be run through a tumbler, bulk sorter and/or stacker.
But the shipping, warehousing, tumbling, sorting and/or stacking operations may dislodge and separate the previously nested preforms. If the preforms become separated, re-assembly is necessary, defeating the purpose of nesting. Previous attempts include: US 2012/0132607, U.S. Pat. Nos. 6,499,311, 6,649,121, 8,851,322 and 9,162,372.
An aerosol container having a bag therein may be made from a dual layer preform, having plural layers disposed one inside the other. Relevant attempts in the art include U.S. Pat. Nos. 3,450,254; 4,330,066; 6,254,820; RE 30093 E; WO 9108099 and US 2011/0248035 A1. But some of these attempts rely upon blow molding the inner and outer preforms together. But this operation may not be suitable if charging without a bung hole is desired or tolerance stackup is to be avoided. And some of these attempts rely upon mechanical block of the inner preform by the shoulder of the outer preform, to prevent separation. But this geometry is not suitable if a smaller shoulder is desired.
It is necessary to join the nested preforms in a way that prevents separation during operations which occur between nesting and blow molding. But such joining should be simple, to overcome the problems associated with trying to automate joining using interlocks and similar compound motion. This invention is directed to the problem of unintended separation of nested preforms.